Selective monomethylation of phenolic compounds

Abstract

Mono-, di- and triphenols are selectively monomethylated by reaction with para-dimethoxybenzene in the presence of a catalytically effective amount of an acid catalyst.

What is claimed is: 
     
       1. A process for the monomethylation of a phenolic compound, comprising reacting as the sole alkylation agent para-dimethoxybenzene with a phenol of the formula: ##STR4## in which R is H, OH, alkyl, alkoxy, halogen, phenyl, alkyl-substituted phenyl, or CF 3 , and R' is H, alkyl, C 6  H 4  OH or C 6  H 4  O-alkyl, in the presence of a catalytically effective amount of an acid catalyst. 
     
     
       2. The process as defined by claim 1, said acid catalyst comprising a liquid acid. 
     
     
       3. The process as defined by claim 2, said liquid acid comprising sulfuric acid. 
     
     
       4. The process as defined by claim 1, said acid catalyst comprising solids having cation exchange capacity. 
     
     
       5. The process as defined by claim 1, comprising reacting equimolecular amounts of said phenol of formula (I) with para-dimethoxybenzene at a temperature ranging from about 80° C. to about 400° C. 
     
     
       6. The process as defined by claim 5, carried out at a temperature ranging from 150° C. to 250° C. 
     
     
       7. The process as defined by claim 1, wherein said phenol of formula (I), R and R' are H and OR' is in a position ortho- or para- with respect to the OH group. 
     
     
       8. The process as defined by claim 2, carried out in the presence of 0.05 g to 0.5 g of concentrated acid per 5 mmol to 50 mmol of para-dimethoxybenzene. 
     
     
       9. The process as defined by claim 4, carried out in the presence of 1 g of solid catalyst having an exchange capacity of 0.5 milliequivalent/g to 1.5 milliequivalent/g per 5 mmol to 50 mmol of para-dimethoxybenzene. 
     
     
       10. The process as defined by claim 1, carried out in an inert liquid reaction medium. 
     
     
       11. The process as defined by claim 4, said solid catalyst comprising a Lewis or Bronsted acid. 
     
     
       12. The process as defined by claim 4, said solid catalyst comprising a clay, zeolite, cation exchange resin, oxide or heteropolyacid.